Pulse jet burner



July 6,1965 i F. HAAG 3,192,986

PULSE JET BURNER Filed Nov. 4, 1963 I 2 Sheets-Sheet 1 F/GJ' ff, fr/f/l."95 25) 52 /a 1/l V5 JE /5 |01 l ,zz al 25*- gig l` Il l 5 H E "f f6 .90'l el l l J Jn' l D /a \i J y 55 J5 ""5 ef" fa' afa l l; ed'

Il. I i Mfr/w09 i l 7 Fem/z Hai@ L 2" 1| 2 344mm f .fbi/af hf@ iframe-yJuly 6, 1965 F. HAAG 3,192,986

PULSE JET BURNER Filed Nov. 4, 1963 2 Sheets-Sheet 2 3,192,986 PatentedJuly 6', 1965 3,19%?86 PULSE JET BR Franz Haag, Plochingen (Neckar),Germany, assigner to Junkers & Co. @adhd-., W ernau (Neclrar, GermanyFiled Nov. 4, 1963, Ser. No. 321,134 Claims priority, applicationGermany, Nov. 10, 1%2,

einen. (ci. rss-4) The present invention relates to apparatus forheating fluids, such as water or air, and more particularly to animproved pulse jet burner which may be used in such apparatus as a meansfor generating heat energy.

Water and air heaters which comprise one or more pulse jet burners (alsocalled resonance duct burners) are known in the art. Such burners mustbe absolutely airtight to prevent escape of combustion products into thesurrounding atmosphere. Furthermore, it is equally important to reducethe noise to a bearable level so that a heater embodying one or morepulse jet burners may be used in homes without being a source ofirritation to the occupants. lt must be borne in mind that a pulse jetburner operates at elevated pressures and that, in the absence of anysoundprooiing, the noise might reach an undesirable level. Heretofore,the noise was combatted by large quantities of expensive sound absorbingmaterial but, to my knowledge, the results obtainable with such materialwere quite unsatisfactory.

Accordingly, it is an important object of my invention to provide animproved pulse jet burner which is constructed and assembled in such away that the noise produced on combustion of a fuel-oxygen mixture isreduced to a level which is very satisfactory to warrant the use of suchburners in private homes, and wherein such substantial reduction innoise is achieved with minimal quantities of sound absorbing material.

Another object of the invention is to provide a pulse jet burner of thejust outlined characteristics which is constructed and assembled with aview to prevent escape of any noxious gases into the surroundingatmosphere, which is of very compact and space-saving design, which maybe used in room heating and/or water heating systems, and wherein eachnoise-generating element or component is shieldedV by at least onesilencer.

A further object of the invention is to provide a novel soundprooiing orsilencing arrangement for the combustion chamber and for the resonanceduct of a pulse jet burner.

With the above objects in view, one feature of my invention resides inthe provision of a duid heating apparatus which comprises a pulse jetburner and heating pipe means arranged to convey fluid to be heated intoan inner soundproong space so that the fluid may exchange heat with oneor more combustion chambersV which are accommodated in the soundprooingspace. The pulse jet burner comprises an outer shell which deiines anouter Soundproong space, an inner shell which is surrounded by the outersoundproofing space and which deiines the inner soundprooiing space, atleast one combustion chamber mounted in the inner shell so as to be atleast partially surrounded by the inner soundproong space, suction ductmeans arranged to deliver a mixture of oxygen and fuel into thecombustion chamber so that the mixture is combusted and heats thechamber when the burner is in operation, and resonance duct meansarranged to convey from the combustion chamber spent gases which developon combustion of the mixture. The outer shell has an inlet which admitsoxygen or oxygen-containing air into the outer soundprooiing space, andthe inner shell is provided with port means through which oxygen oroxygencontaining air is drawn into the inner soundproofing space toenter the open intake of the suction duct means and to be mixed withfuel which is delivered by a supply conduit extending through the shellsand into the inner soundproofing space.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims.v Theimproved pulse jet burner itself, however, both as to its constructionand its method of operation, together with additional features andadvantages thereof, will be best understood upon perusal of thefollowing detailed description of certain specific embodi- V ments withreference to the accompanying drawings, in

which:

FIG. l is a central vertical section through a fluid heating apparatusincluding a pulse jet burner which embodies one form of my invention;

FIG. la is a fragmentary central Vertical section through a slightlymodied pulse jet burner;

FIG. 2 is a horizontal section as seen in the direction of arrows fromthe line lI-Il of FIG. l and illustrates the upper portion of atwo-piece partition which is located below the discharge end of theresonance duct;

FIG. 3 is a horizontal section as seen in the direction of arrows fromthe line llI--lll of FIG. l and illustrates the lower portion of thispartition;

FIG. 4 is a horizontal section as seen in the direction of arrows fromthe line IV--IV of FIG. 1 and illustrates the construction of thelowermost part'of the inner shell; and Y FIG. 5 is a perspective view ofthe lower portion of the inner shell with the cylindrical wall partiallybroken away.

Referring to the drawings, and first to FIG. 1, there is shown a fluidheating apparatus including a pulse jet or resonance duct burner whosecombustion chamber lll serves to heat a continuous stream of fluid(e.g., water or air) which is conveyed through a delivery pipe 25. Thefluid flows through a heating pipe 27 which is coiled around thecombustion chamber 16 and the thus heated fluid is thereupon led awaythrough an evacuating pipe 26; While iiowing through the convolutedheating pipe 27, the fluid exchanges heat with the wall of the chamber1l) which is heated on explosion of gaseous or pulverulent fuel admittedthrough a supply conduit 13. This supply conduit 13 discharges into asuction duct 11 which communicates with the upper end of the chamber 1t)and whoseV open intake sucks oxygen or oxygen-containing air from anupper compartment 14 deiined by the upper portion of an inner housing orshell 15 when the burner is in operation. In accordance with one featureof my invention, the combustion chamber 10 is accommodated in thecompartment 14 and is spaced from the walls of the inner shell 15. Thelatter is provided with a rst sealed opening 23 for the supply conduit13 and with two additional sealed openings 24, 24a for the pipes 25, 26.The combustible mixture which is formed in the suction duct 11 entersthe interior of the combustion chamber 10 and is exploded in rapidsequence. Following each explosion, a sound wave and a column of spentgas will travel down a tail pipe or resonance duct 12 which extendsthrough a sealed opening 29 provided in a horizontal partition 21located in a plane which is perpendicular to the axis of the inner shell15 and serving to separate the upper compartment 14 from a lowercompartment 20. The operation of the pulse jet burner is well known inthe art and by itself forms no part of my invention.

The upper compartment 14 in the inner shell 15Vcon-V stitutes a firstsoundprooiing or silencing space of the improved pulse jet burner, andthis space is surrounded by a second soundproofing or silencing space 19defined by an outer housing or shell 16 which surrounds the inner shell.In the embodiment of FIG. l, the inner shell 15 Vassumes the form of anupright cylinder whose walls are spaced from the Walls ofthe outer shellso that the outer soundprooiing space 19 surrounds the` entire innershell. As shown, the interior of the inner shell l5 accommodates notonly the combustion chamber lil but also the convoluted heating pipe 27,the suction duct 11, a portion of the supply conduit 13, and theresonance duct 12. The open end of the resonance duct 12 discharges intothe lower compartment 2! whence the spent gas advances into a take-olfpipe 2S in a manner to be described in connection with FGS. 2 to 5.

The outer shell 16 comprises a cupped front section 17 which isdetachably but sealingly secured to a panshaped rear section 1 by anelastic coupling 3u disposed in a vertical plane and serving to permitexpansion or contraction of the outer shell depending on the momentarypressure in the outer` shell soundprooling space 19. Thus, and if thepressure in the space i9 rises, the mixture of fuel and air cannotescape from the outer shell 16 because the coupling 3l, expands. Thesealing action may be provided by an annular gasket 39a.

The just described construction of the outer shell 16 is oF particularimportance when the burner is started or when the operation o the burneris not entirely satisfactory. For example, and it it should happen thatthe supply conduit 13 develops a leak, a combustible mixtureV of fueland oxygen will penetrate into the outer soundproofing space 19 andmight even explode to send a column of spent gas into the surroundingatmosphere. Such gas could escape through the inlet were it not for theteature that the outer shell 1.6 may expand to compensate for variationsin pressure prevailing in the space 11. The same result can be achievedby mounting the gasket 3tlg in such a way that it opens a path forescape of fluid into the surrounding atmosphere when the pressureprevailing in the space 19 reaches an undesirably high magnitude.

Y The material et the shells l5, te may be comparatively thin to reducethe cost and the weight of the burner.

The interior of the inner shell l5 actually several distinctsoundprooi'ing or silencing spaces Vone of whichV (the upper compartment14) absorbs noise which develops when the mixture of uel and air isdrawn into and through the suction duct 1l and the other of which (thelower compartment 2i?) absorbs noise which develops when columns orspent gas are discharged through the resonance duct 12. lt was foundthat such construction of the pulse jet burner, especially incombination with the outer shell 16, reducesV noise suliiciently towarrant the utilization of such burners in the wr"e1heating androom-heating systems ot one, two or multi-family dwellings.

In the structure of FlG. l, the partition 21 is located at a levelslightly below the discharge opening of the combustion chamber il?,i.e., somewhat below the intake end of the resonance duct 12. inaccordance with a slight modlcation oi my invention which is shown inPEG. la, the partition 21' may be coplanar with the bottom wallof thecombustion chamber 19 so that the entire resonance duct 12 is located inthe lower compartment 2G. The lowermost convolution of the heating pipe27 extends substantially diametrically across the interior of thecombustion chamber lit so that the fluid flowing through the evacuatingpipe 26 is heated to a very high temperature. Such heating is enhancedby fins or ribs 27a provided on the lowermost convolution ofthe pipe 27.

The compartment 14 communicates with the space 19 through a connectingport 22 which is provided in the top wall of the inner shell 15, and therear section 18 of the outer shell 16 is formed with an air-admittinginlet 31 which delivers air into the space 19 whence the air may ow intothe compartment 14 via port 22 to enter the open intake of the suctionduct 11. The rear section 18 of the outer shell 16 is further formedwith a irst sealed opening 32 for the supply conduit 13, with a pair ofsealed openings 34, 34a for the pipes 25, 26, and with a fourth sealedopening 33 for the take-oft pipe 2S.

It will be noted that spent gas discharged by the resol nance duct 12cannot flow directly into the take-ott pipe 28. This is due to the factthat the improved burner comprises a further soundproofing compartmentor space 55 in the lowermost part of the inner shell 15 which is sealedfrom the compaitment 26 by a horizontal partition 35 whose componentparts are illustrated in FIGS. 2 and 3. The partition 35 deiines anannular channel 36 which conveys spent gas into an annular soundproofingspace 37 extending between the partition 35 and the bottom Wall of theinner shell 15. The lower portion of this annular space 37 communicateswith the intake end of the take-off pipe 28 which extends, through thebottom wall of the inner shell 15, through the lower part of the space19 and through the sealed opening 33.

The partition 35 comprises an upper disk-shaped portion 41 which isshown in FIG. 2 and whose underside is provided with an annulardepression or groove 43 of semicircular cross section. The portion 41 isformed with one or more apertures 46 enabling spent gas to ow from thecompartment 2 into the channel 36. The lower disk-shaped portion 42 ofthe partition 35 is illustrated in FG. 3, and the upper side of thislower portion is provided with an annular depression or groove 44 whichregisters with the groove 43 so that the two grooves together theaforementioned annular channel 36 which is of circular cross section.The second portion 42 is further provided with one or more apertures 47permitting spent gas to dow into the annular space 37. The aperires 46,47 shown in FGS. 2 and 3 are staggered with reference to each other andare separated by an upright battle which compels spent gas entering at46 to iiow through the major part of the channel 36 prior to passingthrough the aperture 47 and into the annular space 37. ln other words,spent gas must travel in an arc of nearly 360 degrees prior to escapingthrough the aperture 47 and into the lowermost compartment 55 of theinner shell 15. lt goes without saying that the aperture 46 or 47 may bereplaced by two or more smaller apertures which may be spaced from eachother in the longitudinal direction of the channel 36. The distancebetween the apertures 46, 47 will determine the color of the sound whichis being produced by spent gas.

The aperture 47 is 4located at a level above an enlarged portion 43 ofthe space 36 (see FIGS. 4 and 5) whose major portion 49 is bounded bytwo bodies of suitable sound absorbing material including a solidcylindrical inner body 51 and a hollow cylindrical outer body 51a Thespace 37 further comprises a second enlarged portion 5t) which extendsupwardly from the intake end of the take-oil pipe 2S. The inner andouter sides of the entire annular space 37 are bounded by perforatedmetallic sheets 54 best shown in FIG. 5. The noise produced by spent gasdischarged from the resonance duct 12 is reduced to acceptable levelwhile the gas must pass through the aperture 46 into the channel 36,thereupon into the annular space 37 via aperture 47, and finally intoand through the take-oft pipe 28.

The supply conduit 13 comprises two enlarged portions 52 and 53 one ofwhich is outwardly adjacent to the outer shell 16 and the other of whichis located in the compartment 14 close to the section ductll. Theenlarged portions 52, 53 and the intermediate portion 13a between theseenlarged portions define a further soundprooting or silencing space.

If it should happen that the inner shell 15 develops a leak in theregion of the lower compartment 20, spent gas might penetrate into theouter space 19 but it thereupon sucked through the connecting port 22 toenter the upper compartment 14 and to be admitted into the combustionchamber 1u. Thus, even if such a leak should develop, spent gas is stillprevented from entering the atmosphere around the outer shell 16 of theburner. As long as the leak is small, spent gas returned into thesuction pipe 11 will have little elfect on the combustion; however, ifthe leak is substantial, the fuel-air mixture might not contain enoughoxygen and the combustion of such mixture is then terminated in a fullyautomatic way. The situation is the same if a leak develops in the wallof the combustion chamber. The gases escape into the compartment 14 andare sucked through the open intake of the duct 11. The operation of theburner will be brought to a standstill if the leak in the combustionVchamber is large enough to reduce the percentage of oxygen in thecombustible mixture below a minimum value.

It goes without lsaying -that the inner shell 16 may accommodate two ormore combustion chambers and an equal number of suction ducts andresonance ducts without in any way departing from the spirit of myinvention. A twin combustion chamber which may be used in the pulse jetburner of the present invention is disclosed in my copending applicationSerial No. 212,048, filed July 24, 1962, to which `reference may be hadif necessary.

The sound absorbing spaces defined by the shells and 15 reduce the noiseto an acceptable level even though the improved pulse jet burnerutilizes Very small quantities of sound absorbing material. The use ofsuch material may be restricted solely to the third compartment 55 inthe lowermost zone of the inner shell 15 which means that the weight ofthe burner is rather small.

The compartment 14 and the surrounding portion of the outersoundprooiing space 19 will form an effective barrier to the noise whichdevelops in the combustion chamber 1l?, in the suction duct 11 and inthe supply conduit 13. The same applies to the silencing action of thecompartments 20, 55 and the lower portion of the space 19 which willreduce noise produced by spent gases in the duct 12, channel 36 andannular space 37. The provision of the soundproong space dened by theenlarged portions 52, 53 and intermediate portion 13a of the supplyconduit 13 is' an additional feature of my invention.

The composition of sound absorbing bodies 51, 51a may be made out ofslag or mineral wool or the like.

Without further analysis, the foregoing will so fully reveal the gist ofthe present'invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpointof prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is: l

1. In a pulse jet burner, in combination, a shell defining a closedsoundprooing space; port means in said shell forming an inlet for anoxygen-containing gaseous medium into said soundprooing space; acombustion chamber arranged entirely within said soundprooing space sothat combustion gases possibly escaping from said combustion chamberthrough a leak therein will enter said soundproong space; a suction ductconnected at one end to said combustion chamber, said suction ductpassing therough said soundprooling space and through said shell so thatit inlet end which is adapted to receive fuel is located outside ofsaidshell, said uction duct having intake opening mean located withinsaid sound-V prooiing space in said shell to receive not onlyoxygencontaining gaseous medium entering said soundproong space throughsaid port means, but also to reconvey into said combustion chamber anycombustible gases which might have escaped from said combustion chamberinto said soundprooing space; and a resonance duct connected to saidcombustion chamber and passing through said shell so `as .to conveyspent gases` from said combustion chamber to the outside of said shell.

Z. A combination as set forth in claim 1, wherein said intake openingmeans of said suction duct located within said soundprooiing space insaid shell is spaced from said port means in said shell.

3. A combination as set forth in claim 1, further comprising heatingpipe means having a portion located in said soundprooiing space in heatexchanging relationship with said combustion chamber and arranged toconvey iiuid to be heated through said space so that the fluid mayexchange heatwith vsaid combustion chamber.

4. A combination asset forth in claim 3, wherein said suction ductcomprises a iirst enlarged portion located externally of said outershell, a second enlarged portion located in said soundprooiing space,and a connecting portion extending between said enlarged portions, saidportions of said suction duct together defining a second soundproongspace.

5. In a pulse jet burner, in combination, an outer shell defining anouter soundproong space; an inner shell accommodated in said outersoundproong 4space and delining a closed inner soundproofing space; portmeans in said inner shell forming an inlet for an oxygen-containinggaseous medium into Isaid linner soundprooing space; a combustionchamber arranged entirely within said inner soundproofing space so thatcombustion gases possibly escaping from said combustion chamber througha leak therein will enter said inner soundproofing space;.a suction ductconnected at one end to said combustion chamber, said suction ductpassing through said inner soundproofing space and through said innershell so that its inlet end which is adapted to receive fuel is locatedoutside of said inner shell, said suction duct having intake openingmeans located within said inner soundproofing space in said inner shellto receive not only oxygen-containing'gaseous medium entering saidinnersoundproong space through said port means, but also to reconveyinto said combustion chamber any combustible gases which might haveescaped from said combustion chamber into said inner soundprooiingspace; :and a resonance duct connected to said combustion chamber andpassing through said inner shell so as to convey spent gases from saidcombustion chamber.

6. ,In a pulse jet burner, in combination, an outer shell defining aclosed outer soundproong space; an inner shell accommodated in saidouter soundprooiing space and defining a second closed soundproongspace, said inner and said outer shells comprising walls which arespaced from each other so that said inner shell is completely surroundedby said outer soundproofing space; rst port means in said outer shellforming an inlet for an oxygen-containing gaseous medium into said outersoundproofing space; second port means'in said inner shell forming aninlet for said medium from said outer space into said innersoundproofing space; a combustion .chamber arranged entirely Within saidinner soundproofing space so that combustion gases possibly escapingfrom said'combustion chamber through a leak therein will entersaid innersoundprooiing space; a suction duct connected at one end to saidcombustion chamber and passing through said inner and outer'shells sothat its inlet end which is adapted to receive fuel is located outsideof said outer shell, said suction duct having inlet opening meanslocated within said inner soundprooiing space to receive not onlyoxygen-containing gaseous medium entering said inner soundproofing spacethrough said second port means, but also to reconvey intosaidrcombustion chamber any combustible gases which might have escapedfrom said combustion chamber into said inner soundprooiing space; and aresonance duct connected to said combustion chamber and passing throughsaid inner and outer shells so as to `convey spent gases from saidcombustion chamber to the outside of said outer shell.

7. In a pulse jet burner, in combination, an outer shell commodated insaid outer soundprooiing space and comsaid outer shell forming an inletfor anY oxygen-containing gaseous medium into said outer soundproofingspace; second port means in said inner shell forming an inlet for saidmedium from said outer space into one of said compartments; a combustionchamber arranged entirely within said one compartment in said innersoundproofing space so that combustion gases possibly escaping from saidcombustion chamber through a leak therein will enter said onecompartment; a suction duct connected at one end to said combustionchamber, said suction duct passing through said one compartment andthrough said inner and outer shells so that its inlet end which isadapted to receive fuel is located outside of said outer shell, saidsuction duct having an intake opening located within said onecompartment and adapted to receive not only oxygencontaining gaseousmedium entering said one compartent through said second port means, butalso to recon- Vey into said combustion chamber any combustible gaseswhich might have escaped from said combustion chamber into said onecompartment; a resonance duct'connected to said combustion chamber'andsealingly extending through said partition, said resonance duct havingan open end arranged to discharge into said other compartment spentgases from said combustion chamber; and a take-ofic pipe connected withsaid inner shell and communicating with said other compartment andextending through said outer soundprooing space and through said outershell to evacuate spent gases from said other compartment to the outsideof said outer shell.

8. A combination as set forth in claim 7, wherein said second port meansis spaced from said first port means so that combustion gases possiblyleaking into said outer soundproong space from said inner soundprooiingspace or from that portion of said take-oil? pipe which passes throughsaid outer soundproofng space will enter said one compartment throughsaid second port means to be reconveyed through said intake opening intosaid combustion chamber.

9. In a pulse jet burner, in combination, a shell defining a closedsoundprooiing space and comprising an internal partition which dividessaid space into a pair of compartments, said shell further having portmeans communicating with one of said compartments and forming an inletfor an oxygen-containing gaseous medium into said one compartment; acombustion chamber arranged entirely within said one compartment so thatcombustion gases possibly escaping from said combustion chamber througha leak therein Will enter said one compartment; a suction duct connectedat one end to said combustion chamber, said suction duct passing throughsaid one compartment and through saidshell so that its inlet end whichis adapted to receive fuel is located outside of said shell, saidsuction duct having an intake opening located Within said onecompartment in such a manner ras to be adapted to receive not onlyoxygencontaining gaseous medium entering said one compartment throughsaid port means, but also to reconvey into said combustion chamber anycombustible gases which might have escaped from said combustion chamberinto said one compartment; a resonance duct connected to saidVcombustion chamber and sealingly extending through said partition, saidresonance duct having an open end arranged to discharge into said othercompartment spent gases from said combustion chamber; and a take-oitpipe connected from said shell and arranged to evacuate spent gases fromsaid other compartment.

10. In a pulse jet burner, in combination, a shell defining a closedsoundproofing space and comprising a first internal partition and anapertured second internal partition, said partitions dividing saidsoundproofing space into three. compartments including a firstcompartment located at one side of said first partition, a secondcompartment located between the other side of said first partition andone side of said second partition, and a third compartment located'atthe other side of said second partition; port means in said shellforming an inlet for an oxygen-containing gaseous medium into said rstcompartment; a combustion chamber arranged entirely within said firstcompartment so that combustion gases possibly escaping from saidcombustion chamber through a leak therein will enter said iirstcompartment; a suction duct connected at one end to said combustionchamber, said suction duct passing through said first compartment andthrough said shell so that its inlet end which is adapted to receivefuel is located outside of said shell, said suction duct having anintake opening located Within said first compartment in said shell insuch a manner as to be adapted to receive not only oxygen-containinggaseous medium entering said first compartment through said port meansbut also to reconvey into said combustion chamber any combustible gaseswhich might have escaped from said combustion chamber into said firstcompartment; a resonance duct connectedy to said combustion chamber andpassing through said first internal partition so as to convey spentgases from said combustion chamber to said second compartment; andtake-off pipe means communicating with said third compartment toevacuate therefrom spent gases which pass into said first compartmentvia said apertured second internal partition.

i1. A combination as set forth in claim 10, wherein said secondpartition defines an annular channel and wherein said third compartmentincludes first and second apertures communicatingly connecting saidchannel with said second and third compartments respectively.

12. A combination as set forth in claim 10, wherein said shell iscylindnical in shape and wherein said partitions are located `in planeswhich are perpendicular to the axis of said shell.

13. A combinationas set forth in claim 11, further comprising bafflemeans mounted in said second partition and extending into said channelfor restricting circulation of spent gas :in said channel, said firstand second apertures being located at the opposite sides of said baiilemeans so that spent gases entering one of said apertures must flowthrough a substantial portion of said channel prior to reaching theother aperture.

'14. A combination as set forth in claim 11, further comprising bodiesof sound absorbing material provided in said third compartment anddefining an annular sound proofing space which communicates with saidchannel via one of said apertures and with said take-olir pipe means.

15. A combination as set forth in claim 14, wherein said annularsoundproofing space includes a first enlarged portion adjacent to saidone aperture and a second enlarged portion adjacent to said take-oitpipe means.

References Cited by the Examiner UNETED STATES PATENTS 2,708,926 5/55Huber et al 60-39.77 X 2,768,031 10/56 Tenney et al 158-4 2,857,33210/58 Tenney et al 158-4 V3,091,224 5/63 Rydberg 158-4 FOREIGN PATENTS1,115,800 l/56 France.

1,057,720 5/59 Germany. 1,688,178 :9/60 Germany.

i JAMES W. WESTHAVER, Primary Examiner.

MEYER PERLlN, Examiner.

1. IN A PULSE JET BURNER, IN COMBINATION, A SHELL BEFINING A CLOSEDSOUNDPROOFING SPACE; PORT MEANS IN SAID SHELL FORMING AN INLET FORM ANOXYGEN-CONTAINING GASEOUS MEDIUM INTO SAID SOUNDPROOFING SPACE; ACOMBUSTION CHAMBER ARRANGE ENTIRELY WITHIN SAID SOUNDPROOFING SPACE SOTHAT COMBUSTION GASES POSSIBLY ESCAPING FROM SAID COMBUSTION CHAMBERTHROUGH A LEAK THEREIN WILL ENTER SAID SOUNDPROOFING SPACE; A SUCTIONDUCT CONNECTED AT ONE END OF SAID COMBUSTION CHAMBER, SAID SECTION DUCTPASSING THROUGH SAID SOUNDPROOFING SPACE AND THROUGH SAID SHELL SO THATIT INLET END WHICH IS ADAPTED TO RECEIVE FUEL IS LOCATED OUTSIDE OF SAIDSHELL, SAID SUCTION DUCT HAVING INTAKE OPENING MEANS LOCATED WITHIN SAIDSOUNDPROOFING SPACE IN SAID SHELL TO RECEIVE NOT ONLY OXYGENCONTAININGGASEOUS MEDIUM ENTERING SAID SOUNDPROOFING SPACE THROUGH SAID PORTMEANS, BUT ALSO TO RECOVERY INTO SAID COMBUSTION CHAMBER ANY COMBUSTIBLEGASES WHICH MIGHT HAVE ESCAPE FROM SAID COMBUSTION CHAMBER INTO SAIDSOUNDPROOFING SPACE; AND A RESONANCE DUCT CONNECTED TO SAID COMBUSTIONCHAMBER AND PASSING THROUGH SAID SHELL SO AS TO CONVEYOR SPENT GASESFROM SAID COMBUSTION CHAMBER TO THE OUTSIDE OF SAID SHELL.